In modern scholarship, the concept of equity is often assimilated with that of Aristotelian epieikeia, a process which serves to correct rules when, though their wording undoubtedly applies to a case, yet the outcome would be unjust, or the legislator would have never wanted the rule to be applied to such a case. My thesis deals with the early-modern origins of the association of equity and epieikeia in legal scholarship, and of its consequences for the doctrinal development of equity in the sixteenth and seventeenth century. I begin by showing that medieval legal writings on equity were almost completely unconcerned with epieikeia, and that the latter was only developed by philosophers and theologians. Legists and canonists developed a concept of equity that was unrelated - indeed mostly incompatible - with judicial discretion or the emendation of written rules. Thus, throughout the Middle Ages, there was almost no interaction between the writings of civil and canon lawyers on equity, and those of theologians on epieikeia. In the second chapter of my thesis, I show that the introduction of epieikeia in legal scholarship was the result of the influence of humanistic philology over the writings of humanist jurists, and argue that it caused the majority of early-modern authors to depart from medieval scholarship on equity, re-modelling instead equity as a doctrine of interpretation of the law beyond its letter in accordance with the intentions of the legislator. The final part of my thesis argues that the development of equity as epieikeia in legal scholarship broke down the barrier that had hitherto divided theological and legal writings on equity. Indeed, from the late sixteenth century onwards, legal and theological writings on equity were connected to such an extent that many later authors treated these two branches of scholarship as belonging to one, equally authoritative body of learning on the same topic.